Recently there have been various glasses-type video display devices in which video displayed on a display device such as a Liquid Crystal Display (LCD) is observed as a virtual image enlarged through an optical system having an eyepiece, a half mirror, or the like. The glasses-type video display devices are called a head-mounted display. For example, WO2004/061519A1 (Patent Document 1) discloses a head-mounted display.
Many video display devices are configured in such a way that they are worn on a face while wrapped around a head. Video display devices are mainly divided into a binocular type in which the video display system is formed at positions corresponding to the eyes and a monocular type in which the video display system is formed at a position corresponding to one of the right and right eyes. Usually the head-mounted display includes a display unit which displays video and a headphone which supplies a sound.
Some of the monocular head-mounted displays can be used while switched between right-eye use and left-eye use. Frequently the right and the left sides of the head-mounted display are interchanged with each other when it is worn on the head depending on whether the head-mounted display is used for the right eye or the left eye. In such cases, the case in which the head-mounted display is used for the right eye differs from the case in which the head-mounted display is used for the left eye in that the right and the left headphones are reversed. Accordingly, it is necessary to reverse right and left audio outputs supplied to the headphones.
In such head-mounted displays, usually it is assumed that sounds supplied from the headphones are heard while video displayed on the display unit is watched. In such cases, the headphone for the right ear and the headphone for the left ear can be distinguished by themselves.
However, depending on usage of the head-mounted display, sometimes the head-mounted display is used to listen to an audio signal alone. In such cases, the video display unit is not located in front of the eye, but sometimes the video display unit is located at a head vertex portion which is of a retracted position far away from the eye. Accordingly, there has been a problem that the right and left switching state of the headphones cannot be recognized only when a shape of the head-mounted display is seen.
In view of the foregoing, a problem to be solved by the present invention is to provide a head-mounted display with which it can be easily determined whether the head-mounted display is used for the left eye or the right eye.